This invention relates to turbine type of power plants and particularly to seal means for the gap existing between the outer air seal of the rotor blades and adjacent vanes for sealing the cooling air in the cooling cavities outboard the gas path therefrom.
Owing to the advent of high performance engine, particularly in light of the concern for fuel conservation there has been an increasing awareness of avoiding air leakages in the engine. Obviously any leakage is in reality a loss of energy and hence adverse to fuel economy.
This invention is directed to the sealing of the gap that exists between the rotor blade, outer air seal and the adjacent vane at the junction point where the outer air seal and vanes are tied to the engine case. I have found that by utilizing a relatively thin ring fabricated from a low thermal expansion material (lower than the case) the forces created by the heated case during expansion forces the ring to bear against the vane structure and outer air seal structure deforming to provide a good seal. This serves to seal the cooling cavities located outboard of the gas path to prevent the higher pressure cooling air from ingressing into the gas path. It is contemplated that the seal be assembled into the engine with a loose fit ring. When the engine is operated, the generated heat causes the case to expand, which is at a rate that is faster than the low expansion seal. This causes the segments of the outer air seal and vane to move in a direction to bear against the seal. At operating temperature the seal is stretched elastically causing it to deform and conform to the contour of the walls of these segments. This gives a good metal to metal contact causing a satisfactory seal.